Method of making a sealable web or sheet product

ABSTRACT

A web or sheet product is provided which is coated on at least a portion of its surface with a bond-enabling material for adhering toner particles on the surface of the sheet. The sheet product can be used as a mailer or confidential form which is sealed using toner particles as the adhesive. The bond-enabling material may be a polymer which is coated on the sheet as a liquid and then cured to form a film on the surface of the sheet. The bond-enabling material is resistant to melting or degrading when exposed to temperatures used for fusing toner particles, and additionally may act as a tie coat to enhance the adhesion of toner particles to the surface of the sheet. The bond-enabling material may be coated on the peripheral edges of the sheet, and toner particles are printed over the bond-enabling material on the peripheral edges of the sheet. The sheet is folded and sealed by the application of heat and pressure to the edges of the sheet.

This is a division of application Ser. No. 08/137,597, filed Oct. 15,1993, now U.S. Pat. No. 5,486,436.

BACKGROUND OF THE INVENTION

This invention relates to a method and apparatus for sealing the edgesof mailers or other business forms, and more particularly to acellulosic or polymeric web or sheet product which is coated on itsperipheral edges with a bond-enabling material. When toner particles areprinted onto the peripheral edges of the sheet over the bond-enablingmaterial, the sheet may be folded and sealed at its edges using thetoner as the adhesive by the application of heat and pressure.

In recent years, mailers and other business forms have been developedfor printing in high speed impact printers which use ribbons forprinting. The forms are typically single-ply continuous forms havingvariable information printed on one surface of the form. During themanufacture of such forms, hot-melt adhesive is applied at selectedmarginal edges of the forms for later use in sealing the forms. Afterprinting, the forms are folded and then passed through a device whichapplies heat and pressure, activating the hot melt adhesive and causingthe folded plies to be sealed together along the their common marginaledges.

However, with the advance of microcomputer technology, business formsand mailers are now printed on a wide variety of commercial printingdevices which are faster, quieter, and more reliable than traditionalmechanical impact printers. Laser printers are an example of a nonimpactprinting device, which operate by turning on and off acomputer-controlled laser beam of light in a specific pattern to form alatent image of static charges on a paper web. The portion of the webcontaining the static charges attracts toner particles and forms a tonerimage, which is then fused on the paper by passing the paper through apair of rolls which apply both heat and pressure to the paper to bondthe toner particles permanently to the paper.

However, mailers and business forms which utilize hot melt adhesives forsealing are not suitable for imaging in laser printers because the hightemperatures required to fuse the toner particles to the paper also meltthe adhesives on the paper, which then become tacky and jam the hotprinter rollers.

An alternative method of sealing in the art involves the use of aself-adhesive or pressure seal made from rubber latex dispersed inwater. When applied to a surface and dried, a film is formed which willnot bond on contact with paper and other surfaces, but will bond oncontact with another film of the same material. These adhesive films areheat resistant and, if properly formulated, do not become tacky to othersurfaces when heated. However, formulation of commercially trouble-freeself-adhesives has not been completely successful. In addition,self-adhesive seals have a short shelf life of about three months orless.

Recently, a number of attempts have been made to utilize the adhesiveproperties of toner particles used in nonimpact printers to seal mailersand other business forms. For example, European patent No. 245424describes a machine for sealing a sheet which has been coated on itsperipheral edges with toner particles by a laser printer. The sheet isfolded in the form of an envelope and then passed through first andsecond sealing zones comprising heated, driven pairs of sealing discswhich heat the toner particles, causing them to become tacky and adhereto each other, thus sealing the sheet.

Swedish Patent Application No. 8505243 also teaches a sheet materialcoated with strips of heat-activatable electronically printed tonerstrips on its edges. The sheet is folded so that the strips come intocontact with each other, then the sheet is advanced through a machinehaving a heating zone which applies heat and pressure to seal the sheetin the form of an envelope.

However, a disadvantage of these methods is that when the toner materialis fused to the paper during the laser printing process, it tends toimpregnate, or sink into the paper so that there is little tonerremaining on the surface of the paper to form a strong bond when thepaper is folded and sealed. As a result, the bond formed by the sealingoperation is very weak, and the mailer may inadvertently open before itreaches the intended recipient.

Accordingly, the need still exists in the art for adhesively bondingboth porous and non-porous surfaces utilizing toner material as anadhesive to provide a strong bond.

SUMMARY OF THE INVENTION

The present invention meets that need by providing a porous or nonporousweb or sheet product and method in which a bond-enabling material iscoated onto the web or sheet so that toner particles which are printedon coated areas of the sheet remain firmly bonded on the surfacethereof. The present invention is applicable to all non-impactingprinting processes, including but not limited to laser, magnetographic,ion deposition and thermal transfer printing, which utilize dry tonerparticles. The areas of the web or sheet printed with toner may becontacted with other areas of the web which have toner printed thereonor with a second web or sheet having toner to provide a sealed businessform or mailer having a strong adhesive bond.

In accordance with one aspect of the present invention, a web or sheetis provided comprising a substrate having two major surfaces.Preferably, at least a portion of one major surface of the sheet iscoated with a bond-enabling material for adhering toner particles on thesurface of the sheet.

In addition to the effectiveness of the bond-enabling coatings of thisinvention when applied to porous substrates such as paper or othercellulosic materials, it has also been discovered that these coatingsare effective when applied to non-porous polymeric substrates such as,for example, polyesters, polycarbonates, polyolefins, cellulose acetate,polystyrene and its copolymers, polyurethanes, polyvinyl chloride,polysulfones and polyimides. In some instances it is desirable to printonto polymeric substrates with printers or copiers which use particulatetoners, and then seal these printed surfaces together. For example,images on transparent film or sheets are used in optical projection, orfor certain label applications. Untreated polymeric films and sheetsnormally do not form strong adhesive bonds with toners used innon-impact printers, at least partly because of the low surface energyof such polymeric surfaces. Adhesion of toners can be greatly enhancedby treating such surfaces with a thin layer of a bond-enabling materialto form a tie coat which serves as a bridge between the surface and thetoner particles normally used in such non-impact printers as laser,magnetographic, ion, and thermal transfer. This enhanced bonding makesit practical for toners to participate in adhesively bonding twopolymeric surfaces previously treated with the bond-enabling coatings ofthis invention.

In accordance with another aspect of the invention, a non-porous web orsheet is provided, comprising a polymeric substrate having two majorsurfaces. At least a portion of one major surface of the web or sheet isprovided with a coating of a bond-enabling material for bonding to tonerparticles. When toner particles are printed onto these coated layers andtwo toner-bearing areas are brought into contact and subjected to heatand pressure, a permanent bond is formed between the two areas, thetoner particles adhering to one another and to the bond-enablingcoatings which serve to bond the toner particles strongly to thesurfaces of the substrates. The adhesive bond which is formed could notbe achieved by the use of either toner alone or by bond-enablingmaterial.

The bond-enabling material comprises a coating which forms a film on thesurface of the sheet, and is resistant to melting or degrading whenexposed to temperatures used for fusing toner images. Preferably, thebond-enabling material is a thermoplastic polymer applied to the sheetat a coating weight of between about 0.3 to 2.0 lb/ream (17″×22″×500sheets), and is applied as a liquid and then dried or cured. In additionto maintaining toner particles on the surface of the sheet, thebond-enabling material may also act as a tie coat to enhance theadhesion of toner particles to the surface of the sheet.

In one embodiment of the invention, the bond-enabling material comprises100% solids ultraviolet curable thermoplastic polymerized orpolymerizable material selected from the group consisting of reactivemonofunctional monomeric acrylates, rubber-modified epoxy diacrylateoligomers, and thermoplastic rubbers. The bond-enabling material may beapplied to the web or sheet as a liquid by any conventional printing orcoating processes such as flexographic, gravure, or dry offset printing.The bond-enabling material is then cured by exposure to ultravioletradiation to result in a solid, nontacky coating.

In another embodiment of the invention, the bond-enabling materialcomprises a copolymer of styrene and acrylic acid and a crosslinkingagent.

In yet another embodiment of the invention, the bond-enabling materialis selected from the group consisting of carboxylated styrene-butadienelatexes, styrene-butadiene latexes, alkyd resins, olefin waxes andemulsions, acrylic resins, phenolic resins, and polyvinyl alcohol. Thebond-enabling materials of the present invention are effective for useon both porous and nonporous cellulosic and polymeric substrates.

In a preferred embodiment of the invention, toner particles are printedonto the peripheral edges of the sheet containing the bond-enablingmaterial. The sheet is then sealed by folding the sheet so that at leasta portion of its peripheral edges align, and heat and pressure areapplied to the peripheral edges of the sheet.

The sheet product may optionally include printed indicia on at least oneof its major surfaces and form a business form or mailer. In addition,the sheet may include a cut out window so that when it is folded andsealed, a portion of the printed indicia is visible through the cut outwindow. Thus, the sheet may be printed in a single pass through aprinter without having to print address information on the outside ofthe form. In another embodiment of the invention, the sheet may includeperforations located inside at least one of the peripheral edges of thesheet so that the sealed edges may be removed for opening of the maileror business form.

In an alternative embodiment of the invention, the sheet product is notfolded for sealing, but rather is sealed to a second sheet having acoating of the bond-enabling material on at least a portion of one majorsurface thereof. After application of toner to one or both sheets, thesecond sheet is collated on top of the first sheet product such thattheir respective coated areas are in contact, and the two sheets aresealed together by applying heat and pressure. The sheet product mayinclude printed indicia on at least one of its major surfaces. Inaddition, a die cut window may be provided on the second sheet so thatindicia printed on the first sheet is visible through the window whenthe sheets are sealed.

A method for making the sheet product is also provided which generallycomprises the steps of providing a web or sheet having two majorsurfaces, and coating a portion of one major surface of the sheet with abond-enabling material for adhering to the toner particles on thesurface of the sheet. Toner particles are printed on the coated areas ofthe sheet surface, and the sheet is then folded and sealed by theapplication of heat and pressure on the coated areas.

An alternative method of making the sheet product comprises the steps ofproviding a first web or sheet having two major surfaces, and coating aportion of one major surface of the sheet with a bond-enabling materialfor adhering to toner particles on the surface of the sheet. Toner isthen printed on the coated areas of the sheet surface. A second sheethaving two major surfaces is provided which is coated with thebond-enabling material on the corresponding areas of one major surface.The second sheet is then collated on top of the first sheet such thattheir coated areas are in contact, and their respective coated areas aresealed by the application of heat and pressure.

The present invention thus provides a mailer or business form which maybe effectively sealed by using toner as an adhesive in combination witha bond-enabling material which prevents the toner from sinking into thesurface of the sheet and also enhances the adhesion of toner to thesheet surface. Accordingly, it is an object of the present invention toprovide a web or sheet product coated with a bond-enabling material foradhering toner particles, when printed on the surface of the sheet toimprove sealing of the sheet using the toner as the adhesive.

It is also an object of the present invention to provide a polymeric webor sheet product coated with a bond-enabling material which provides anadhesive bridge between toner particles and a polymeric surface whentoner is printed on the surface of the sheet, to improve sealing of thesheet using toner as the adhesive. These, and other objects andadvantages of the present invention will become apparent from thefollowing detailed description, the accompanying drawings, and theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the printing, folding andsealing steps of the present invention;

FIG. 2 is a schematic perspective view of a device for folding andsealing the web or sheet product of the present invention;

FIG. 3 is a front plan view of a sheet product in accordance with thepresent invention;

FIG. 4 is an alternative embodiment of the sheet product illustrated inFIG. 3; and

FIG. 5 is a front plan view illustrating the folded, sealed product ofthe present invention in the form of a mailer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred sheet product of the present invention is illustrated inFIG. 3 and comprises a cellulosic substrate 10 having two majorsurfaces. The sheet may be cellulosic or polymeric, and either porous ornonporous. At least a portion of the peripheral edges of one majorsurface of the sheet are coated with a bond-enabling material 12 formaintaining toner particles printed on the peripheral edges of thesheet. The bond-enabling material may optionally be coated on the entiresurface of the sheet to act as a tie coat to enhance the adhesion of alltoner indicia printed on the sheet surface.

The bond-enabling material comprises a polymer which forms a film on thesurface of the sheet, and is preferably coated on the sheet as a liquidand then dried or cured. Preferably, the bond-enabling material isapplied to the sheet at a coating weight of between about 0.3 to 2.0lb/ream (17″×22″, 500 sheet ream). In addition to maintaining tonerparticles on the surface of the sheet, the bond-enabling material mayact to enhance the adhesion of toner particles to the surface of thesheet and is resistant to melting, or degrading when exposed totemperatures used for fusing toner images. Typical temperatures used intoner fusing rolls range from about 250° F. to above 300° F.

In one embodiment of the invention, the bond-enabling material comprisesan ultraviolet curable thermoplastic polymerized or polymerizablematerial selected from the group consisting of reactive monofunctionalmonomeric acrylates, rubber-modified epoxy diacrylate oligomers, andthermoplastic rubbers. The bond-enabling material may be applied to thesubstrate as a liquid by any conventional printing or coating processessuch as flexographic, gravure, or dry offset printing. The bond-enablingmaterial is preferably applied to the substrate at a coating weight ofbetween about 0.8 and 1.2 lb/ream. The bond-enabling material is thencured by exposure to ultraviolet radiation to result in a solid,nontacky coating. See commonly assigned, copending U.S. application Ser.No. 07/822,680, filed Jan. 21, 1992, and entitled Radiation CurableToner Adhesion-Enhancing Composition and Coated Product, the disclosureof which is hereby incorporated by reference.

In another embodiment of the invention, the bond-enabling materialcomprises a copolymer of styrene and acrylic acid and a crosslinkingagent. The bond-enabling material is preferably applied to the web as anaqueous dispersion and then dried by conventional means as discussed inU.S. Pat. No. 5,045,426, the disclosure of which is hereby incorporatedby reference. Preferably, the bond-enabling material is applied to thesubstrate at a coating weight of between about 0.3 and 1.0 lb/ream, andmost preferably about 0.6 lb/ream.

In yet another embodiment of the invention, the bond-enabling materialis selected from the group consisting of carboxylated styrene-butadienelatexes, styrene-butadiene latexes, alkyd resins, olefin waxes andemulsions, acrylic resins, phenolic resins, and polyvinyl alcohol. Thebond-enabling material is applied at a coating weight of from about 0.3to about 2.0 lb/ream, and preferably between about 0.5 to about 1.0lb/ream. For this embodiment of the invention, the bond-enablingmaterial preferably is as taught in Pinell et al, copending U.S.application Ser. No. 07/339,972, filed Apr. 18, 1989, and entitled TonerAdhesion Enhancing Coating and Coated Paper, the disclosure of which ishereby incorporated by reference. Other bond-enabling materials usefulin the practice of the present invention are taught in U.S. Pat. Nos.5,102,737 and 5,017,416, the disclosures of which are incorporated byreference.

As shown in FIG. 3, toner particles 14 are then printed on theperipheral edges of the sheet on the bond-enabling material. As shown inFIG. 5, the toner particles 14 may be printed in the form of a stripedpattern on the peripheral edges of the sheet. By printing toner in sucha striped pattern, less toner is required to achieve effective adhesionbecause the toner stripes overlap and/or criss-cross once the sheet isfolded. However, it should be appreciated that a number of differenttoner patterns may be printed on the sheet which result in an effectiveseal such as angled stripes or cross-hatched stripes. Descriptions ofnoncontact printers useful in the present invention such as laserprinters, the toners used therein, and the papers used for printing onthem are known. See, for example, “New Papers for New Printers,”Chemtech (1986), the disclosure of which is hereby incorporated byreference. Other nonimpact printers such as magnetographic, iondeposition, and thermal transfer printers may also be used in thepractice of the invention.

As shown in FIG. 3, the sheet product may optionally include printedindicia on at least one of its major surfaces. The indicia may consistof repetitive indicia 30 which can be pre-printed on the form or mailerusing conventional flexographic or lithographic printing processes.Non-repetitive, individualized indicia 32 such as name, address, billingamounts, etc. may also be printed on the form or mailer by the nonimpactprinter at the same time the toner edges are printed.

As shown in FIG. 4, the sheet may also include a cut out window 16 sothat when the sheet is folded and sealed, a portion of the printedindicia is visible through the cut out window. Transparent plasticwindow 18 is optional. The sheet may also include perforations 20located inside at least one of the peripheral edges of the sheet so thatthe sealed edges may be easily removed for opening.

FIG. 6 illustrates an alternative embodiment of the invention in whichthe sheet 10 is sealed to a second sheet 40 having two major surfacesand optionally having a coating of the bond-enabling material 12 on theperipheral edges of at least one of its major surfaces. The second sheetis collated on top of the sheet product such that their respectivecoated edges are in contact, and the two sheets are sealed along theirrespective peripheral edges by applying heat and pressure. The sheetproduct may include printed indicia on at least one of its majorsurfaces, and a die cut window 16 may be provided on the second sheet sothat indicia printed on the sheet product is visible through the window.

FIG. 1 illustrates a method of making one embodiment of the web or sheetproduct of the present invention which comprises the steps of providinga web or sheet 10 with a coating on the peripheral edges of one majorsurface of a bond-enabling material 12. The bond-enabling material maybe printed or coated onto the web by any of a number of conventionaltechniques including printing by means of a flexographic press, offsetgravure coating, direct blade coating, roll coating, or air knifecoating. Further, the coating may be applied directly on the paper bythe use of a gate roll, twin gate roll, blade, or bill blade coaters.The sheet is then passed through a nonimpact printer 34 where tonerparticles 14 are printed on the peripheral edges of the sheet andnon-repetitive indicia is also printed. The sheet may then require asecond pass through the printer to print the address information on theopposite surface of the sheet. Alternatively, if a cut out window isincluded on the sheet, it may be printed in a single pass. The sheet isthen passed through a folding apparatus 36 which folds the sheet alongat least one of its major axes. Finally, a sealing apparatus 38 appliesheat and pressure to the edges of the sheet to fuse the toner particlesand seal the sheet. European patent No. 245424 and Swedish patentapplication No. 8505243, both of which are incorporated herein byreference, describe suitable sealing mechanisms for sealing the sheet orsheets of the present invention.

FIG. 2 schematically illustrates a typical folding and sealing apparatuswhich may be used for the web or sheet product of the present invention.The sheet 10 having indicia (not shown) already printed thereon isadvanced through a folding means 22, and is then advanced between feedrollers 24 and through a sealing means which includes a heating element(not shown) and sealing rollers 26 and 28 through which the sheet issequentially passed.

An alternative method of making the sheet product comprises the steps ofproviding a first web or sheet having two major surfaces, and coating aportion of one major surface of the sheet with a bond-enabling materialfor adhering toner particles on the surface of the sheet. Tonerparticles are then printed on the coated areas of the sheet surface. Asecond sheet having two major surfaces is provided which is coated withthe bond-enabling material and optionally toner on the coated areas ofone major surface. The second sheet is then collated on top of the firstsheet such that their coated areas are in contact, and their respectivecoated areas are sealed by the application of heat and pressure.

The cellulosic or polymeric product of the present invention may have avariety of potentially useful applications. For example, the presentinvention may be used to seal mailers or business forms printed with alaser or other nonimpact printer without the need for hot melt adhesivesor self-adhesives. In addition, the present invention may be used toprovide a means for ensuring the confidentiality of information receivedby facsimile transmission in which a laser printer is utilized. Thepaper to be printed with information by facsimile is coated on at leastits peripheral edges with the bond-enabling material. The laser printeris programmed to print toner on the peripheral edges of the papersimultaneously with information transmitted by facsimile. The laserprinter may be provided with means for folding the output sheet andapplying heat and pressure in the manner illustrated in FIG. 2. The faxsheet may also include a cut out window so that when folded, theintended recipient's name is visible through the window.

As an alternative to folding the fax sheet, a second sheet having thebond-enabling coating on at least its peripheral edges may be sealed tothe fax sheet as a cover sheet. The printer may be provided with meansfor collating the two sheets and applying heat and pressure to seal thesheets together. A cut out window may be provided on the second sheet sothat the recipient's name is visible through the window after it issealed to the sheet product. The sealed information may then be exposedby peeling the sealed portions from each other or by cutting or tearingaway the peripheral edges of the sheets.

While the drawings show the bond-enabling coating at the peripheraledges of the form or mailer sheets, it should be understood thatbond-enabling material may be coated in any convenient areas of thesheets consistent with the design and use of the forms or mailers, andmay be even coated over the entire area of one surface.

While certain representative embodiments and details have been shown forpurposes of illustrating the invention, it will be apparent to thoseskilled in the art that various changes in the methods and apparatusdisclosed herein may be made without departing from the scope of theinvention, which is defined in the appended claims.

What is claimed is:
 1. A method of making a web or sheet productcomprising the steps of: providing a web or sheet having two majorsurfaces, coating a portion of one major surface thereof with abond-enabling material for adhering toner particles on the surface ofsaid sheet, printing toner particles on said coated areas of said sheet,folding said sheet along at least one major axis and sealing said foldedsheet by the application of heat and pressure to said folded sheet tofuse said toner particles.
 2. The method of claim 1 wherein said sheetincludes printed indicia on at least one major surface thereof.
 3. Themethod of claim 2 wherein said sheet includes a cut out window such thatwhen said sheet is folded and sealed, a portion of said printed indiciais visible through said cut out window.
 4. The method of claim 1 inwhich said web or sheet comprises a cellulosic substrate.
 5. The methodof claim 1 in which said web or sheet comprises a polymeric substrate.6. The method of claim 1 in which said bond-enabling material is coatedat a coating weight of between about 0.3 to 2.0 lb/ream.
 7. The methodof claim 1 in which said bond-enabling material comprises an ultravioletcurable thermoplastic polymerized or polymerizable material selectedfrom the group consisting of reactive monofunctional monomericacrylates, rubber-modified epoxy diacrylate oligomers, and thermoplasticrubbers.
 8. The method of claim 1 in which said bond-enabling materialcomprises a copolymer of styrene and acrylic acid and a crosslinkingagent.
 9. The method of claim 1 in which said bond-enabling material isselected from the group consisting of carboxylated styrene-butadienelatexes, styrene-butadiene latexes, alkyd resins, olefin waxes andemulsions, acrylic resins, phenolic resins, and polyvinyl alcohol.